Patent GB-900211-A (GB)
Title: Improvements relating to antennas
IPC: H01Q21/06
Filed: 1958-07-29
Abstract: 900,211. Aerial systems. TYNER CORPORATION. July 29, 1958 [July 29, 1957], No. 24455/58. Class 40(7). The invention relates to arrays of end-fire elements producing a retarded surface wave effect and each consisting of a plurality of metallic members spaced between an eighth and a half of the working wavelength apart along an axis about which each member is symmetrically arranged. The major dimension of each element is between a quarter and a half of the working wavelength and energy launching means are symmetrically arranged about one end of each axis for propagating energy along the element axes. According to the invention the launchers are fed with energy of the same phase and the elements are spaced between 360 degrees and apart, where L is the length of the elements in wavelengths. In the design of a directional array it is desirable to obtain a high gain, narrow beam width, and low side lobe levels in a minimum physical size of array. A discussion of the design problem is given using the " element factor pattern " and the " array pattern characteristic " as a means of analyzing the direction pattern produced by a particular arrangement of elements of a particular length. It is noted that it has previously been proposed to restrict the element spacing to the range between 160 and 320 electrical degrees (see U.S.A. Specification 2,955,287), the reason for the 320 degrees limitation being the production of large side lobes at large angles from the main lobe. It has, however, been found that where the element factor pattern offers low side lobe levels a useful design field with element spacing in excess of 320 degrees is available. Two cases are discussed in one of which the element pattern never rises above 22 db. below the peak level beyond the first side lobe and in the other of which the second (but no succeeding) side lobes are above the 22 db. level but an array factor peak occurs near the null between the first and second element side lobes. In both of these the maximum allowable element spacing is determined by the need to ensure that the second array factor peak from the desired direction does not occur closer than the 22 db. level on the side of the first element side lobe nearest the second element side lobe. It is shown that this maximum element spacing is Where the launchers are fed with energy of equal amplitude it is stated to be desirable to provide between 2 and 16 elements of between 2 and 12 times the wavelength in length. In the case of an array having a tapered amplitude feed between 3 and 18 elements may be used of a length of from 2 to 15 wavelengths. Whilst a linear array of parallel elements is primarily considered a stack of such arrays may be provided or the elements in a linear array may have their axes directed upwards and downwards alternately from a reference plane at equal acute angles (Figs. 7, 8 and 9, all not shown). One suitable form of radiating element is shown in Fig. 3 and comprises a flat supportmember 65, preferably metallic, carrying rectangular wire mesh elements 63 and fed by a dipole launching device 62 mounted in front of a metallic mesh reflector 61. Another form of element comprising metallic discs 22 mounted on a rod 20 is shown in Fig. 4. This element is energized by a waveguide cavity 24 and the way in which it and a number of parallel elements can be supported by a rigid structure of conductive rods is indicated.